Seung Wan Kim

Decentralized Vehicle-to-Grid Design for Frequency Regulation within Price-based Operation

The utilization of electric vehicles has been suggested to support the frequency regulation of power system. Assuming that an intermediate aggregator exists, this study suggests a decentralized vehicle-to-grid operation scheme in which each vehicle-to-grid aggregator can behave independently of the power system operator. To implement this type of decentralized operation, this study adopts a price-based operation that has been proposed by many researches as an alternative operation scheme for the power system. In this environment, each vehicle-to-grid aggregator can determine its participation in vehicle-to-grid service in consideration of its residual energy of aggregated system and real-time market price. Consequently, the main purpose of this study is to verify whether or not the vehicle-to-grid power can effectively support the current frequency regulation function within the price-based operation scheme. Specifically, a frequency regulation method is proposed based on the real-time price signal, and a feedback controller for battery management is designed for decentralized vehicle-to-grid operation.

Economic benefit of energy storage system for frequency regulation

To address the environmental concerns throughout the world, many new power sources, such as renewable energy, are being introduced. In order to maintain the reliability and stability of the system while integrating these inputs, many systems have started integrating battery energy storage systems. However, the introduction of such system has been very slow due to its high capital costs. Therefore, the economic benefit of a lithium ion battery energy storage system used for frequency regulation in a utility company is analyzed. The profit of a utility is calculated in terms of reduced amount of power purchase cost, and the results verify that the utility is able to recover their investments within the life cycle of the storage system in all cases.

A Priority Index Method for Efficient Charging of PEVs in a Charging Station with Constrained Power Consumption

The sizable electrical load of plug-in electric vehicles may cause a severe low-voltage problem in a distribution network. The voltage drop in a distribution network can be mitigated by limiting the power consumption of a charging station. Then, the charging station operator needs a method for appropriately distributing the restricted power to all plug-in electric vehicles. The existing approaches have practical limitation in terms of the availability of future information and the execution time. Therefore, this study suggests a heuristic method based on priority indexes for fairly distributing the constrained power to all plug-in electric vehicles. In the proposed method, PEVs are ranked using the priority index, which is determined in real time, such that a near-optimal solution can be obtained within a short computation time. Simulations demonstrate that the proposed method is effective in implementation, although its performance is slightly worse than that of the optimal case.

Contractual Framework for the Devolution of System Balancing Responsibility from the Transmission System Operator to Distribution System Operators

The goal of this research is to trigger the devolution of the system balancing responsibility entirely belonging to the transmission system operator (TSO) to several local distribution system operators by fairly allocating system balancing cost based on a cost-causality principle. Within the devolved system balancing scheme, distribution system operators (DSOs) have appropriate motivation for reducing the variability and uncertainty caused by units in their own area. As the number of renewable electricity sources (RES) being connected to the local distribution system increases, it would be advantageous for the TSO to share the increasing burden of the system balancing responsibility with multiple DSOs. To achieve this, we suggest that, first DSOs be designated as the representatives of their own jurisdictions with primary economic responsibility for balancing payments that are originally charged to each energy market participant. Second, this research proves that a cost-causality based cost allocation scheme(CC-CAS) is superior to an energy-amount based cost allocation scheme (currently widely used) in terms of economic efficiency. Additionally, to avoid the side effect that a DSO with a large amount of RES may face a high and risky balancing payment under the CC-CAS, this research also proposes an optimal balancing payment insurance (BPI) contract which helps the DSO hedge the risks associated with uncertain balancing payments.

Framework for determining the compensation price for output curtailment of distributed generation within active distribution network management

Within active distribution network management, distributed generations, which are contracted by the non-firm connection method, can be directly controlled by the distribution network operator to adjust their power factor and the active power output level. This is called an output curtailment of distributed generation. Although the purpose of the output curtailment is to stably operate the distribution network, it inevitably limits the revenue of distributed generations. Therefore, the need for suitable compensation to the output curtailment is often discussed. As an extension to the discussion, this study proposes the method to determine the suitable bounds of the compensation price for output curtailment. In the proposed method, the suitable bounds of compensation price are obtained from the profit analysis of stakeholders in accordance with the level of the compensation price through optimal power flow technique.